arash,
This is from Microsoft. I have copied and pasted it for you below:
Windows Auditing Issue
Auditing is a vital step in detecting system intrusions or malicious
activity on your systems and network. The Windows Event Viewer does not log
event entries in the security log unless you enable auditing on the system.
Solution
Enable auditing on each Microsoft® Windows® operating system on your
network. After you enable auditing, you can choose which events to monitor,
such as successful or failed logon attempts. In addition, certain files and
directories can be audited on NTFS file systems for modifications or
deletions. View the links under the Additional Resources section below for
more information on configuring audit policies.
Instructions
To enable auditing on a computer running Windows Server "Longhorn", Windows
Server 2003, Windows Vista, Windows XP, or Windows 2000
Open the Control Panel.
In Control Panel, double-click Administrative Tools, and then click Local
Security Policy.
In Local Security Settings, double-click Local Policies, double-click Audit
Policy, and then click the events that you want to audit. We recommend that
you audit the following events:
Audit account logon events (Success, Failure)
Audit account management (Success, Failure)
Audit directory service access (Failure)
Audit logon events (Success, Failure)
Audit object access (Failure)
Audit policy change (Success, Failure)
Audit system events (Success, Failure)
To view the event logs, click Start, point to Programs, point to
Administrative Tools, and then click Event Viewer.
Additional Resources
Chapter 3 - Audit Policy (Threats and Countermeasures Guide)
Chapter 9 - Auditing and Intrusion Detection (Securing Windows 2000 Server)
Windows Server 2003: Auditing Security Events Best Practices
©2002-2007 Microsoft Corporation. All rights reserved.
I hope this helps you.
C.B.